U.S. patent application number 13/819775 was filed with the patent office on 2013-06-27 for multiphase converter comprising magnetically coupled phases.
This patent application is currently assigned to ROBERT BOSCH GMBH. The applicant listed for this patent is Nils Draese, Mirko Schinzel. Invention is credited to Nils Draese, Mirko Schinzel.
Application Number | 20130162225 13/819775 |
Document ID | / |
Family ID | 44509398 |
Filed Date | 2013-06-27 |
United States Patent
Application |
20130162225 |
Kind Code |
A1 |
Draese; Nils ; et
al. |
June 27, 2013 |
MULTIPHASE CONVERTER COMPRISING MAGNETICALLY COUPLED PHASES
Abstract
Disclosed is a multiphase converter comprising multiple phases
(11 to 16), each of which can be triggered using switching means
(21 to 26), at least one phase (11) being magnetically coupled to
at least three other phases (12, 14, 16) by corresponding coupling
means (31, 36, 37).
Inventors: |
Draese; Nils; (Feuerbach,
DE) ; Schinzel; Mirko; (Stuttgart, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Draese; Nils
Schinzel; Mirko |
Feuerbach
Stuttgart |
|
DE
DE |
|
|
Assignee: |
ROBERT BOSCH GMBH
Stuttgart
DE
|
Family ID: |
44509398 |
Appl. No.: |
13/819775 |
Filed: |
August 26, 2011 |
PCT Filed: |
August 26, 2011 |
PCT NO: |
PCT/EP2011/064766 |
371 Date: |
February 28, 2013 |
Current U.S.
Class: |
323/218 ;
323/355 |
Current CPC
Class: |
H02M 3/1584 20130101;
H01F 2038/026 20130101; H02M 2001/0064 20130101 |
Class at
Publication: |
323/218 ;
323/355 |
International
Class: |
H02M 3/04 20060101
H02M003/04; H01F 38/00 20060101 H01F038/00; H03H 7/18 20060101
H03H007/18 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 3, 2010 |
DE |
10 2010 040 202.8 |
Claims
1. A multiphase converter, comprising a plurality of phases (11 to
16), each of which can be driven by one of a plurality of switches
(21 to 26), characterized in that a plurality of couplers (31, 36,
37) are provided, which magnetically couple at least one phase (11)
to at least three further phases (12, 14, 16).
2. The device as claimed in claim 1, characterized in that one
phase (11) is coupled to a further phase (14) for at least partial
compensation of the DC component of the current profile.
3. The device as claimed in claim 1, characterized in that the
plurality of switches (21 to 26) drive the phases (11 to 16)
sequentially, and in that one phase (11) is magnetically coupled to
at least one further phase (12, 16) driven directly previously and
subsequently.
4. The device as claimed in claim 1, characterized in that one
phase (11) is mechanically coupled to at least one further phase
(12, 16) having a directly preceding and succeeding switch-on or
switch-off instant.
5. The device as claimed in claim 1, characterized in that one
phase (11) is magnetically coupled to at least one further phase
(14) driven in a manner phase-shifted approximately
180.degree..
6. The device as claimed in claim 1, characterized in that exactly
six phases (11 to 16) are provided, wherein the plurality of
couplers (31 to 39) magnetically couple each of the six phases (11
to 16) to three further phases of the six phases (11 to 16).
7. The device as claimed in claim 1, characterized in that at least
three phases (11, 13, 15) run spatially in a first plane and in
that at least three further phases (12, 14, 16) run spatially in a
second plane, which is parallel to and spaced apart from the first
plane.
8. The device as claimed in claim 1, characterized in that at least
one phase (11, 13, 15) is embodied in a U-shaped, rectangular and
meandering fashion.
9. The device as claimed in claim 1, characterized in that the
phases (11 to 16) are constructed as leadframes and as part of a
printed circuit board (70).
10. The device as claimed in claim 1, characterized in that at
least two phases (11, 12) to be coupled can be driven with
different current directions at least in the region in which they
are enclosed by the coupling means (31).
11. The device as claimed in claim 1, characterized in that the
plurality of switches (21 to 26) drive the phases (11 to 16)
sequentially, and in that one phase (11) is magnetically coupled to
at least one further phase (12, 16) driven directly previously.
12. The device as claimed in claim 1, characterized in that the
plurality of switches (21 to 26) drive the phases (11 to 16)
sequentially, and in that one phase (11) is magnetically coupled to
at least one further phase (12, 16) driven directly
subsequently.
13. The device as claimed in claim 1, characterized in that one
phase (11) is mechanically coupled to at least one further phase
(12, 16) having a directly preceding switch-on or switch-off
instant.
14. The device as claimed in claim 1, characterized in that one
phase (11) is mechanically coupled to at least one further phase
(12, 16) having a directly succeeding switch-on or switch-off
instant.
15. The device as claimed in claim 1, characterized in that at
least one phase (11, 13, 15) is embodied in a U-shaped, rectangular
fashion.
16. The device as claimed in claim 1, characterized in that at
least one phase (11, 13, 15) is embodied in a U-shaped, meandering
fashion.
17. The device as claimed in claim 1, characterized in that the
phases (11 to 16) are constructed as leadframes.
18. The device as claimed in claim 1, characterized in that the
phases (11 to 16) are constructed as part of a printed circuit
board (70).
Description
BACKGROUND OF THE INVENTION
[0001] The invention is based on a multiphase converter of the
generic type. A multiphase converter of the generic type is known
from WO 2009/114873 A1, for example. The DC/DC converter described
therein comprises a coil having a non-linear inductive reactance, a
switching system and an output filter. In this case, adjacent
phases are coupled to one another.
[0002] A converter for converting electrical energy is already
known from EP 1145416 B1. The latter thus proposes that the
inductor size can be reduced by the use of coupled inductances. In
this case, the coupled inductors are intended to be dimensioned
such that the load currents of the partial branches mutually
compensate for one another and do not lead to magnetic loading of
the inductors. Only the differential current between the individual
partial branches then leads to a magnetic field.
[0003] It is an object of the present invention to specify a
multiphase converter which is distinguished by simple producibility
and further reduction of the structural space, in particular by
virtue of a smaller volume of the coupling means, and simple
controllability.
SUMMARY OF THE INVENTION
[0004] The multiphase converter according to the invention has the
advantage over the prior art that a disturbing mutual influencing
of the phases is minimized by the magnetic coupling of one phase to
at least three further phases. In this case, the phases to be
coupled are chosen such that an optimum compensation can be
achieved. This is effected, in particular, by means of a current
profile in opposite directions. In this case, the aim is for the
phases to be magnetically coupled so as to minimize the resulting
magnetic field on account of the coupled phases. It is thereby
possible to have recourse to a coupling means of small design, such
as a ferrite core, for example, for coupling the magnetic fluxes. A
corresponding coupling enabled the magnetic field to be greatly
reduced, such that the corresponding coupling means, for example a
ferrite core, can also be correspondingly reduced in terms of its
mass. In the case of the proposed coupling, the phases can be
driven in order. Relatively simple and thus easily controllable
current profiles arise in this case. Particularly expediently, one
phase--in the case of an arrangement comprising six phases--is
coupled to the two respectively adjacent phases and also to a phase
shifted by 180 degrees. An adjacent phase is understood to be one
which is driven directly previously or subsequently. In the case of
the magnetic coupling proposed, it is furthermore possible for the
individual phases to be driven independently of one another.
[0005] The corresponding multiphase converter also makes it
possible to avoid a complex three-dimensional construction and
instead to have recourse to a substantially two-dimensional
construction.
[0006] By virtue of the fact that coupling means are provided which
magnetically couple at least one phase to at least three further
phases, it is also possible to increase the fail-safety since a
higher interlinking of the phases is obtained by means of the at
least triple coupling, such that the failure of one phase cannot
yet lead to unsafe operating states.
[0007] In one expedient development it is provided that such phases
which have current profiles approximately in antiphase are coupled
to one another. This results in a high level of compensation of the
DC fields, such that the magnetic modulation can be reduced
further. As a further consequence, the coupling means can become
smaller or an air gap can be dispensed with.
[0008] In one expedient development it is provided that a first
phase substantially has a planar, U-shaped course, while a second
phase has a substantially rectangular, planar course. These phases
formed in this way can be enclosed by coupling means, preferably
commercially available ferrite cores. As a result, the desired
coupling of at least three phases is achieved in a very simple
manner with recourse to a matrix-shaped construction.
[0009] In one expedient development it is provided that the phases
are embodied as leadframes. This type of production is
distinguished by favorable manufacturing costs. In the case of a
six-phase system, in this case three phases can be embodied in
rectangular fashion and three phases in U-shaped fashion. The same
geometrical shapes can substantially be used, thus making
manufacture even more expedient.
[0010] In one expedient development it is provided that the phases
are part of a multilayered printed circuit board. Thus, the phases
to be coupled to one another can be introduced in a manner
electrically insulated from one another on at least two planes. A
printed circuit board preferably has corresponding cutouts into
which the limbs of the respective coupling means are introduced for
the purpose of magnetically coupling the respective phases.
Expediently, the phases in the case of a printed circuit board can
also be embodied in multilayered fashion with corresponding
parallel connection.
[0011] In one expedient development it is provided that one phase
is coupled to a further phase for at least partial compensation of
the DC component of the current profile. In one particularly
expedient development it is provided that one phase is magnetically
coupled to at least one further phase driven in a manner
phase-shifted substantially by approximately 180.degree.. This
results in a particularly high level of compensation of the DC
fields, such that the magnetic modulation can be reduced further.
As a further consequence, the coupling means can become smaller or
an air gap can be dispensed with. By virtue of this type of
coupling of the phases, the coupling means can be provided in a
geometrically advantageous matrix arrangement. The latter is
distinguished by simple construction, the use of simple coupling
means such as planar ferrite cores, and a small spatial extent.
Moreover, filters can be given smaller dimensions.
[0012] In one expedient development it is provided that the
switching means to drive the phases sequentially, and in that one
phase is magnetically coupled to at least one further phase driven
directly previously and/or subsequently. In one particularly
expedient development it is provided that one phase is magnetically
coupled to at least one further phase having a directly preceding
and/or succeeding switch-on or switch-off instant. In one expedient
development it is provided that one phase is magnetically coupled
to at least two further phases respectively driven directly
previously and subsequently.
[0013] These instances of driving result in relatively simple
current profiles, which can therefore also be controlled relatively
simply.
[0014] In one expedient development it is provided that three
coupling means are provided in order to magnetically couple one of
the phases to three further phases. In one particularly expedient
development it is provided that exactly six phases are provided,
wherein the coupling means magnetically couple each of the six
phases to three further phases of the six phases. This type of
coupling firstly ensures that the individual phases can still be
controlled independently of one another. Moreover, the fail-safety
of the multiphase converter can be increased on account of the
greater interlinking of the phases.
[0015] In one expedient development it is provided that the phases
run spatially substantially on parallel planes. In one particularly
expedient development it is provided that at least three phases run
spatially in a first plane and that at least three further phases
run spatially in a second plane, which is parallel to and spaced
apart from the first plane. This makes possible a construction of
the multiphase converter that is cost-effective and simple in terms
of production engineering, since, in particular, two-dimensional
phase shapes can be used. In one expedient development it is
provided for this purpose that at least one phase is embodied in a
U-shaped, rectangular and/or meandering fashion. By virtue of these
geometries, all couplings of the preferably six phases can be
performed with just two phase shapes, namely U-shaped and
rectangular and/or meandering. By virtue of having recourse to only
two different shapes in the case of preferably six phases, the
proportion of shared components in the arrangement is increased, as
a result of which the manufacturing costs are reduced further. In
one expedient development it is provided that the phases are
constructed as leadframes and/or as part of a printed circuit
board. This type of manufacture is particularly cost-effective. In
the the integration of at least one portion of the phases in a
printed circuit board, further electronic components such as the
switching means can be arranged there. In one expedient development
it is provided that the printed circuit board comprises at least
two, preferably three, cutouts for receiving the coupling means.
This simplifies the positionally correct arrangement of the
coupling means relative to the phases integrated at least partly in
the printed circuit board.
[0016] In one expedient development it is provided that the phase
embodied in a rectangular and/or meandering fashion has at least
one chamfer in the region of a corner. In one expedient development
it is provided that, in the case of at least one of the phases, a
folding region is provided outside the region enclosed by the
coupling means. What is achieved by the measures provided is that
adjacent coupling means can move spatially closer together. This
becomes apparent in a reduction of structural space.
[0017] In one expedient development it is provided that at least
two phases to be coupled are at least partly enclosed by a coupling
means, wherein the phases to be coupled can preferably be driven
with different current directions. Preferably, the phases to be
coupled run run at least partly approximately parallel in the
region enclosed by the coupling means. In one particularly
expedient development it is provided that the coupling means
encloses at least two phases that are to be magnetically coupled in
each case in a first region and in a second region. By virtue of
this chosen type of coupling, it is possible to use standard parts
such as, for example, planar ferrite cores as coupling means. These
could have a rectangular or double-rectangular cross section. In
one expedient development it is provided that the coupling means
are arranged in a matrix-type fashion. Particularly in the case of
a rectangular outer contour of the coupling means, in the case of
the proposed coupling in the case of six phases the new coupling
means required can be arranged in a matrix-type fashion (3.times.3)
and thus in a space-saving and planar fashion. In one expedient
development it is provided that the coupling means comprises at
least two parts, wherein one of the parts has a U-, O-, I- or
E-shaped cross section. By virtue of this construction, the phases
to be coupled can be surrounded by the coupling means in a
particularly simple manner. In one expedient development it is
provided that a gap, preferably an air gap, is provided between two
parts. The inductance can be influenced particularly simply in this
way. In one expedient development it is provided that a plurality
of coupling means consisting of at least two parts have at least
one common part, preferably a metal plate. This could facilitate
assembly since all the coupling means could be closed in only one
step by the placement of the plate.
[0018] In one expedient development it is provided that at least
two, in particular three, coupling means are provided in order to
magnetically couple one of the phases to two further phases,
wherein at least one of the two coupling means has a lower
inductance than the other coupling means. Various aspects can be
influenced and optimized by means of a targeted choice of the
inductance of the coupling means. Firstly, the inductance
influences the power loss and thus also the evolution of heat in
the coupling means. A reduction of the inductance also reduces the
power loss. Moreover, a lower inductance can serve as saturation
protection. As a result, coupling means having a lower inductance
become saturated only later at higher currents, such that in the
case of a fault the multiphase converter can still be operated
longer in a stable operating state. On the other hand, a high
inductance reduces the current ripple. The loss distribution,
saturation behavior and current ripple can thus be optimized with
the choice of the suitable inductance.
[0019] In one expedient development it is provided that the
coupling means which couples one phase to one phase driven in a
manner phase-shifted substantially by approximately 180.degree. has
a lower inductance than at least one of the other coupling means.
As a result, these coupling means, which are generally subjected to
higher loading, can be reduced with regard to the losses, such that
a reduced evolution of heat is also obtained.
[0020] In one expedient development it is provided that three
coupling means are provided in order to magnetically couple one of
the phases to three further phases, wherein at least one of the
three coupling means has a lower inductance than the other two
coupling means. Saturation protection is thus realized for one
phase, said saturation protection having a positive effect on the
system stability. Expediently, a coupling means having a lower
inductance should be provided for each of the preferably six
phases. In one expedient development it is provided that the
coupling means is provided with an air gap. The inductance of the
coupling means can thereby be influenced in a particularly simple
manner. If an air gap is provided in the case of an otherwise
identical design of the coupling means, the inductance is reduced
relative to the version without an air gap. This can be effected
particularly expediently by the middle one of the three limbs of
the coupling means being shortened relative to the two outer limbs,
such that an air gap forms there.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] A number of exemplary embodiments are illustrated in the
figures and are described in greater detail below.
[0022] In the figures:
[0023] FIG. 1 shows a circuit arrangement,
[0024] FIG. 2 shows a schematic illustration of the respective
coupling of the phases,
[0025] FIG. 3 shows the spatial arrangement of the various phases
and coupling means,
[0026] FIG. 4 shows a section through a coupling means with two
coupled phases,
[0027] FIG. 5 shows two typical configurations of the phases in
accordance with the exemplary embodiment according to FIG. 3,
[0028] FIG. 6 shows a further exemplary embodiment with seven
phases,
[0029] FIG. 7 shows the driving and current profiles in the case of
the exemplary embodiment in accordance with FIG. 1,
[0030] FIG. 8 shows the temporal current profiles of the first
phase 11 and fourth phase 14 and underneath the difference between
the two currents,
[0031] FIG. 9 shows one basic possibility of coupling three
phases,
[0032] FIG. 10 shows an alternative exemplary embodiment with
folded phases and at the bottom the associated plan view,
[0033] FIG. 11 shows a further alternative exemplary embodiment
with chamfered meandering phases,
[0034] FIG. 12 shows an alternative exemplary embodiment of a
coupling means with an air gap, and
[0035] FIG. 13 shows one possible realization of the exemplary
embodiment according to FIG. 3 with a printed circuit board.
DETAILED DESCRIPTION
[0036] The construction of a multiphase converter 10 is illustrated
in terms of circuitry in accordance with FIG. 1. The multiphase
converter 10 described here by way of example consists of six
phases 11 to 16. Each of the phases 11 to 16 can be driven
individually via corresponding switching means 21 to 26, each
consisting of a high-side switch and a low-side switch. On account
of magnetic coupling to three further phases, each current of the
phases 11 to 16 flows through three inductances Lxx brought about
by the corresponding coupling means 31 to 39. A first coupling
means 31 magnetically couples the first phase 11 to the second
phase 12, thus resulting in an inductance L12 for the first phase
11 and an inductance L21 for the second phase 12. A sixth coupling
means 36 magnetically couples the first phase 11 to the sixth phase
16, thus resulting in an inductance L16 for the first phase 11 and
an inductance L61 for the sixth phase 16. A seventh coupling means
37 magnetically couples the first phase 11 to the fourth phase 14,
thus resulting in an inductance L14 for the first phase 11 and an
inductance L41 for the sixth phase 16. A second coupling means 32
magnetically couples the second phase 12 to the third phase 13,
thus resulting in an inductance L23 for the second phase 12 and an
inductance L32 for the third phase 13. A ninth coupling means 39
magnetically couples the second phase 12 to the fifth phase 15,
thus resulting in an inductance L25 for the second phase 12 and an
inductance L52 for the fifth phase 15. A third coupling means 33
magnetically couples the third phase 13 to the fourth phase 14,
thus resulting in an inductance L34 for the third phase 13 and an
inductance L43 for the fourth phase 14. An eighth coupling means 38
magnetically couples the third phase 13 to the sixth phase 16, thus
resulting in an inductance L36 for the third phase 13 and an
inductance L63 for the sixth phase 16. A fourth coupling means 34
magnetically couples the fourth phase 14 to the fifth phase 15,
thus resulting in an inductance L45 for the fourth phase 14 and an
inductance L54 for the fifth phase 15. A fifth coupling means 35
magnetically couples the fifth phase 15 to the sixth phase 16, thus
resulting in an inductance L56 for the fifth phase 15 and an
inductance L65 for the sixth phase 16.
[0037] An input current I.sub.E is distributed among the six phases
11 to 16. At the input, a capacitor as filter means is connected to
ground. The outputs of the phases 11 to 16 are combined at a common
summation point and connected to ground by means of a capacitor
(not designated more specifically) as filter means. The output
current I.sub.A is then present at the common output-side summation
point. The inductances Lxx respectively coupled to one another are
oriented with different winding senses with respect to one another,
as indicated by the corresponding dots in FIG. 1.
[0038] FIG. 2 systematically illustrates how the six phases 11 to
16 are coupled to one another by corresponding coupling means 31 to
39. As already described in conjunction with FIG. 1, not only are
adjacent phases coupled to one another but also additionally the
phase offset by 180 degrees. An adjacent phase is understood to be
one which is driven temporally directly previously or subsequently,
that is to say has temporally directly preceding or succeeding
switch-on instants. In the exemplary embodiment here the
designation of the phases 11 to 16 is chosen such that the phases
11 to 16 are driven successively in accordance with the numbering,
that is to say in the order (indications correspond to the
reference signs of the phases): 11-12-13-14-15-16-11, etc., in each
case in a manner phase-shifted by 60 degrees or by T/6 (360
degrees/number of phases), wherein T represents the period duration
of a drive cycle. This order is also shown in FIG. 2 and FIG. 7.
That is to say that the start instants for the various phases 11 to
16 are phase-shifted by 60 degrees in each case or temporally
shifted by T/6 in each case. In FIG. 7, although the respective
phase is switched off again after the temporal duration T/6 (PWM
ratio 1/6), depending on the desired voltage ratio the switch-off
could be effected earlier or later, through to duration-on Te,
depending on the desired PWM signal (between 0% (duration-off,
Te=0) and 100% (duration-on, Te=T), relative to a period duration
T).
[0039] FIG. 3 then schematically depicts the matrix-like spatial
construction of the concept shown in FIG. 2. In this case, the
coupling means 31 to 39 are preferably embodied as planar coil
cores, for example ferrite cores, which each have two cavities. In
said cavities of the coupling means 31 to 39, in each case two
conductors or phase sections of two phases to be coupled are
enclosed, which have different current directions in these
sections, as indicated by the arrows.
[0040] Referring also to FIG. 5, it is possible to discern two
geometrical shapes of phases 11 to 16 or busbars or conductors of
the phases 11 to 16. The first phase 11, third phase 13 and fifth
phase 15 are embodied in a U-shaped fashion. These three phases 11,
13, 15 preferably all run in the same plane. In a further plane
parallel to and spaced apart therefrom--above in the exemplary
embodiment in accordance with FIG. 3--there run the second, fourth
and sixth phases 12, 14, 16. The second, fourth and sixth phases
12, 14, 16 are embodied in a rectangular or meandering fashion. In
this case, they are arranged such that they are enclosed with the
phase to be coupled in each case, U-shaped phase 11, 13, 15, in the
respective coupling means 31 to 39 with a different current
direction.
[0041] Referring to the sectional illustration in FIG. 4, the
coupling illustrated in FIG. 3 is explained by way of example on
the basis of the first phase 11 and the second phase 12. The first
coupling means 31 consists of an E-shaped first part 44 and a
plate-shaped second part 43, which form the coil cores. The limbs
of the first part 44 having an E-shaped cross section are all of
the same length, such that they can be closed by the plate-shaped
(I-shaped cross section) second part 43 without an air gap. The
preferably strip-shaped section of the first phase 11 is in each
case introduced in the lower region of the coupling means 31. These
sections of the first phase 11 shown lie in the same plane, that is
to say are planar with respect to one another. The current
direction corresponds to that current direction indicated by arrows
in accordance with FIG. 3. The second phase 12, preferably likewise
embodied in a strip-shaped fashion, then becomes situated in the
respective overlying region of the first coupling means 31. On the
other side of the first coupling means 31, in the further cavity
thereof, first and second phases 11, 12 are led through with a
respective opposite current direction relative to the current
direction in the other cavity. In the case of the first coupling
means 31, this is effected by virtue of the fact that both the
first phase 11 and the second phase 12 are led back again at the
upper end side of the first coupling means 11 in a 180 degrees bend
through the other cavity. The two sections of the second phase 12,
which are enclosed by the first coupling means 31, are also
situated in the same plane, that is to say are embodied in a planar
fashion. The plane of the first phase 11 and the plane of the
second phase 12 are embodied such that they are parallel to and
spaced apart from one another at least in the inner region of the
first coupling means 31.
[0042] The first phase 11 and the second phase 12 are then
magnetically coupled to one another by the first coupling means 31.
The antiparallel current routing indicated achieves the effect of
keeping the resulting magnetic field as low as possible, such that
the size of the coupling means 31 can be minimized. Moreover,
between the first phase 11 and the second phase 12 a respective
insulation 45 is provided for electrically isolating the two phases
11, 12 from one another and in each case with respect to the
coupling means 31.
[0043] The second phase 12 is coupled to the third phase 13 via the
second coupling means 32 in the same way. Moreover, the second
phase 12 is coupled to the fifth phase 15 by means of the ninth
coupling means 39. The further corresponding couplings can be
gathered from FIG. 3 and will not be described separately
again.
[0044] The exemplary embodiment in accordance with FIG. 6 differs
from that according to FIG. 3 merely in that a further, seventh
phase 17 is also provided. This seventh phase 17 is in each case
magnetically coupled to the first phase 11 by the tenth coupling
means 40, to the third phase 13 by the eleventh coupling means 41
and to the fifth phase 15 by the twelfth coupling means 42. This
exemplary embodiment is intended to illustrate that other
multiphase systems having a different phase number than n=6 can
also be used, without dispensing with the basic concept of the at
least triple coupling, whilst maintaining a suitable matrix-type,
substantially two-dimensional arrangement.
[0045] The diagram in accordance with FIG. 7 shows the temporal
profiles of the drive signals 52 for the respective switching means
21 to 26 of the corresponding phases 11 to 16 and the current
profiles in the phases 11 to 16. The switching means 21 to 26
energize the associated phases 11 to 16 successively for in each
case one sixth of a period duration T, for example by means of a
PWM signal, and are subsequently freewheeling. The resultant
current profiles of the individual phases 11 to 16 are shown by way
of example underneath. The period duration T of the drive signals
52 is of the order of magnitude of 0.01 ms, for example. The start
instants for the various phases 11 to 16 are phase-shifted by 60
degrees in each case or temporally offset by T/6. The start instant
of the second phase 12 with the corresponding drive signal 52 of
the second switching means 22 is at t=0 and is switched off again
(depending on the desired PWM ratio) after 1/6 T. The start instant
of the third phase 13 adjacent to the second phase 12 is at T/6,
the start instant of the fourth phase 14 is at 2T/6, and so on.
Although in FIG. 7 the respective phase is switched off again after
T/6 (PWM ratio 1/6), depending on the desired voltage ratio the
switch-off could be effected earlier or later, through to
duration-on, depending on the desired PWM signal (between 0%
(duration-off) and 100% (duration-on)). That is to say that at a
specific instant a plurality of phases 11 to 16 could also be
energized simultaneously if this is required by the desired voltage
ratios. However, the start instants are temporally offset.
[0046] FIG. 8 shows the temporal current profiles of the first
phase 11 and of the fourth phase 14 and underneath the difference
between the two currents I res. In this case, it is evident that,
relative to the first phase 11, the current profile of the fourth
phase 14 is distinguished by the DC components largely running in
opposite directions. The DC fields cancel one another out for the
most part, as can be gathered from the lower curve I res in FIG. 8.
Therefore, a coupling of the first phase 11--alongside a coupling
to the adjacent phases 12, 16--to the fourth phase is particularly
advantageous.
[0047] A further basic possibility for coupling three phases 11,
14, 16 is shown in FIG. 9. In this case, the first phase 11 and the
sixth phase 16 energized in the opposite direction are enclosed by
a sixth coupling means 36' enclosing these two conductor sections.
The first phase 11 and the fourth phase 14 energized in the
opposite direction are enclosed by a seventh coupling means 37'.
The coupling means 36', 37' have an O-shaped, or respectively
rectangular cross section.
[0048] The exemplary embodiment according to FIG. 10 differs
relative to that according to FIG. 3 in that the ends of the
busbars of the phases 11 to 16 are folded in folding regions 60,
indicated by arrows, as soon as they are led out from the interior
of the coupling means 31 to 39. As a result, the coupling means, in
FIG. 10 in each case those bearing the reference signs 39, 35; 35,
34; 32, 38; 38, 33, can move closer together. In this case, the
meandering busbars of the respective phases 11 to 16 can also be
bent up at the sides. As a result, the meanders can also be pushed
into one another, as illustrated in the left-hand lateral schematic
diagram in plan view. The U-shaped leadframes of the third and
fifth phases 13, 15 would then have to run into different planes,
however, for example by means of corresponding bending.
[0049] In the exemplary embodiment in accordance with FIG. 11, the
phases 12, 14, 16 running in a meandering fashion are provided with
chamfer regions 62 at the corners, such that preferably straight
sections arise, in order to lead adjacent phases 12, 16 parallel to
one another at a small distance in said chamfer regions 62. As a
result, the coupling means 32, 38 and 39, 35 can likewise be pushed
closer together.
[0050] The exemplary embodiment according to FIG. 12 differs from
that according to FIG. 4 in that the middle limb of the E-shaped
first part 44 has an air gap 64 in the direction of the second part
43.
[0051] The exemplary embodiment according to FIG. 13 discloses one
possible realization of the exemplary embodiment according to FIG.
3. First, third and fifth phases 11, 13, 15 are integrated in a
printed circuit board 70, said phases running in a U-shaped fashion
substantially in accordance with FIG. 5. The meandering phases 12,
14, 16 are arranged on the surface of the printed circuit board 70.
The printed circuit board 70 has a multiplicity of rectangular
cutouts 72. Three cutouts 72 are respectively coordinated with the
geometry of the three limbs of the coupling means 31 to 42. For the
second coupling means 32', the three limbs of the first part 44
having an E-shaped cross section have already been inserted from
below through the three cutouts 72 and project upward beyond the
plane of the printed circuit board. The meander of the second phase
12 is fed around the middle limb for the purpose of magnetic
coupling to the U-shaped third phase 13 situated in the printed
circuit board 70. The magnetic circuit of the coupling means 31 is
closed by placement of the second part 43. This is shown by way of
example for the first coupling means 31, in the case of which the
plate-shaped second part 43 has already been placed onto the three
limbs of the first part 44.
[0052] The exemplary embodiments described operate in the manner
explained in greater detail below. Multiphase converters 10 or
DC/DC converters having high powers without special insulation
requirements can preferably be realized in multiphase arrangements.
The high input current I.sub.E, for example with a magnitude of 300
A, is thereby distributed among the various six phases 11 to 16
with a magnitude of 50 A in each case. As a result of the
subsequent superposition of the individual currents to form an
output current I.sub.A, it is possible to obtain a smaller AC
current component. The corresponding input and output filters in
accordance with FIG. 1, depicted as capacitors by way of example,
can then turn out to be correspondingly small. The phases 11 to 16
are driven sequentially, that is to say successively, such that the
switch-on instants are phase-shifted in each case by 60 degrees (or
temporally by T/6) (in the case of the six-phase system described),
as has already been shown in greater detail in FIG. 7. Depending on
the desired voltage ratios, the respective phases 11 to 16 are
energized with different durations. The corresponding high-side
switch of the switching means 21 to 26 is closed for this purpose.
The phase 11 to 16 is not energized if the corresponding low-side
switch of the switching means 21 to 26 is closed. Alternatively,
such phases 11 to 16 having directly preceding or succeeding
switching-off instants could also be regarded as adjacent. The
corresponding switch-on points would then be chosen variably
depending on the desired PWM signal.
[0053] A respective phase 11 is then magnetically coupled together
with at least three further phases 12, 14, 16, to be precise in
such a way that the DC components of the individual phases are in
each case compensated for by other phases to the greatest possible
extent. This reduces the resulting magnetic field, such that the
coupling means 31 to 39 or the magnetic circuit need be designed
only substantially with regard to the magnetic field generated by
the AC component. As a result, the coupling means 31 to 39 such as
coil cores, for example, can be given correspondingly small
dimensions, which leads to considerable savings in respect of
coupling material, mass and costs. In particular the structural
space can be greatly reduced as a result.
[0054] Alongside the two phases that are adjacent with regard to
the driving (switch-on and/or switch-off instants), the third phase
to be coupled is then preferably chosen in such a way that a
disturbing mutual influencing of the phases is minimized. The
choice is made such that an optimum compensation of the DC current
component is obtained. In this case, it has been found that
alongside the adjacent phases (+/-60 degrees phase shift of the
switch-on instants in the case of six phases; for the first phase
11, the adjacent phases would therefore be the second phase 12 and
the sixth phase 16) the phase having a phase offset of 180 degrees
(for the first phase 11, this would be the fourth phase 14) is also
particularly suitable since a very high extinction of the DC
component arises there. FIG. 8 shows the temporal current profiles
of the first phase 11 and fourth phase 14 and underneath the
difference I res between the two currents. In this case, it is
evident that, relative to the first phase 11, the current profile
of the fourth phase 14 is distinguished by the DC component largely
running in an opposite direction. Therefore, a corresponding
further magnetic coupling of the first phase 11 to the fourth phase
14 is suitable. The two currents through the coupled phases 11, 14
flow oppositely in the seventh coupling means 37. In this case, the
resulting current I res for the magnetization of the coupling means
37 is initiated only by the difference between the currents I res.
The DC fields cancel one another out for the most part. The reduced
DC component becomes apparent in a positive way for the geometry of
the coupling means 31 to 39, which can now manage with a smaller
volume. In the case of six phases 11 to 16, the coupling shown in
FIGS. 1 to 3 has proved to be particularly suitable.
[0055] Magnetic Coupling
[0056] In principle, two phases can be magnetically coupled by the
two phases being led with antiparallel current routing through a
rectangular or ring-shaped coupling means 31 to 41. What is
essential is that the coupling means 31 to 41 is able to form a
magnetic circuit. This is possible in the case of a substantially
closed structure, which can also comprise an air gap. Furthermore,
the coupling means 31 to 41 consists of a magnetic-field-permeable
material having suitable permeability.
[0057] One basic possibility for coupling three phases 11, 14, 16
is shown in FIG. 9. In this case, the first phase 11 and the sixth
phase 16 energized in the opposite direction are enclosed by a
sixth coupling means 36' surrounding these two conductor sections.
The first phase 11 and the fourth phase 14 energized in the
opposite direction are enclosed by a seventh coupling means 37'. In
the case of this coupling possibility, respectively half a turn of
two phases 11, 16; 11, 14 are coupled to one another. The coupling
means 36', 37' can be correspondingly composed for example of one
part having a U- and I-shaped cross section or of two parts having
a U-shaped cross section. As is shown in conjunction with FIGS. 3
and 4, however, an arrangement that is particularly advantageous
geometrically is possible when using coupling means having E- and
I- or E- and E-shaped cross sections with a whole turn in each
case.
[0058] The coupling concept underlying FIG. 3 can be explained by
way of example with reference to FIG. 4. What is essential is that
the phases to be coupled--they are the first phase 11 and second
phase 12 in accordance with FIG. 4--are driven with a current flow
in opposite directions. The respectively corresponding magnetic
fields substantially cancel one another out with regard to their DC
component, such that predominantly only the AC component
contributes to magnetic field generation. Consequently, the
corresponding coupling means 31 to 41 can become smaller or an air
gap can be dispensed with.
[0059] One possible concept for realizing the exemplary embodiment
in accordance with FIG. 3 could consist of a printed circuit board
70 into which the nine coupling means 31 to 39, here preferably
planar cores, are embedded, as shown in FIG. 13. All the switching
means 21 to 26, in each case consisting of high-side or low-side
MOSFETs as possible exemplary embodiments, can be integrated on
said printed circuit board 70. The windings for the first, third
and fifth phases 11, 13, 15 can also be integrated into said
printed circuit board 70. The other windings of the second, fourth
and sixth phases 12, 14, 16 could be realized by means of a more
cost-effective copper leadframe. Alternatively, the further
windings of the second, fourth and sixth phases 12, 14, 16 could
also be integrated in the printed circuit board 70.
[0060] Realizations in which all windings are embodied in the form
of copper rails or printed circuit boards would likewise be
possible. A further advantage of the construction in accordance
with FIG. 3 consists in the short paths of the phases 11 to 16
through all coupling means 31 to 39, and the simple construction
without crossovers.
[0061] Construction of Coupling Means
[0062] The coupling means 31 to 41 are means for inductive coupling
such as, for example, an iron or ferrite core of a transformer, on
which the phases 11 to 16 to be coupled generate a magnetic field.
The coupling means 31 to 42 closes the magnetic circuit of the two
coupled phases 11 to 16.
[0063] The choice of the material of the coupling means 31 to 38
and of the permeability does not play such a major part for the
coupling. If no air gap is used, the permeability of the magnetic
circuit rises, as a result of which the inductance of the coil
increases. As a result, the current rise becomes flatter and the
current waveforms approximate more to the ideal DC current. The
closer the waveforms come to a DC current, the smaller the
resulting current difference between the two phases which are led
(oppositely) through a core as coupling means 31 to 42. The outlay
for filters is thereby reduced. On the other hand, a system without
an air gap reacts very sensitively to different currents between
the phases 11 to 16. Although the system tends toward attaining
saturation in the case of smaller current faults, it is
nevertheless still very stable as a result of the multiple
coupling.
[0064] In principle, it is possible to choose air gaps with
different dimensions in order to distribute the losses uniformly
among the coupling means 31 to 42. Coupling means 31 to 42 having a
lower inductance L also have, in principle, a lower power loss.
[0065] In order to obtain a good compromise between high
permeability (no air gap.fwdarw.low current ripple) and high
robustness (with air gap.fwdarw.high current ripple), different air
gaps can be provided. In this way, the power losses of the coupling
means 31 to 42 can also be influenced such that desired criteria
(for example uniform distribution of the power loss) are fulfilled.
In the case of the exemplary embodiment in accordance with FIG. 3,
the coupling means in one of the diagonals (either coupling means
31, 38, 34 or 37, 38, 39) are to be provided with an air gap. As a
result, with only three coupling means 31, 38, 34 or 37, 38, 39
with an air gap (which leads to a higher current ripple) on all the
phases 11 to 16, this gives rise to a high protection against
saturation and, associated therewith, a protection against an
uncontrolled current rise. In the case of a great asymmetry between
the phases 11 to 16 or else upon the failure of a plurality of
phases 11 to 16, only individual coupling means 31 to 42 would
attain saturation, but for a given current not all the coupling
means 31 to 42 of one phase.
[0066] A further variant would be to form the coupling means 31 to
42 within the construction with different air gaps. The coupling
means (in the exemplary embodiment according to FIGS. 1-3, they are
the coupling means bearing the reference signs 37, 38, 39) which
are loaded with a greater increased magnetization on account of the
180 degrees phase-offset driving (such as arises in the case of the
exemplary embodiment according to FIGS. 1-3 by the coupling of the
first phase 11 to the fourth phase 14 by the seventh coupling means
37; coupling of the second phase 12 to the fifth phase 15 by the
ninth coupling means 39; coupling of the third phase 13 to the
sixth phase 16 by the eighth coupling means 38) could be reduced in
terms of their loading for example by adaptation or provision of an
air gap. This would reduce the total core losses.
[0067] Furthermore, it would be possible, in the case of the matrix
concept, in each row/column, to provide one coupling means 31 to 42
with a larger air gap or gap. As a result, this coupling means 31
to 42 provided with an air gap would become saturated only at
higher currents, thus resulting in further improved stability in
the case of a fault. For reasons of stability, it would be
advantageous to lead each phase 11 to 16 through at least one
coupling means 31 to 42, which attains saturation later than the
other coupling means 31 to 42 in this phase as a result of the
provision of a lower inductance L, which could be achieved by the
provision of an air gap.
[0068] An example of a coupling means 31 provided with an air gap
64 is shown in the exemplary embodiment according to FIG. 12. For
this purpose, the middle limb of the E-shaped first part 44 is
embodied in a manner shortened somewhat relative to the outer
limbs, thus giving rise to an air gap 64 in the direction of the
second part 43. Alternatively, provision could be made for
embodying the limbs of the E-shaped first part 44 with an identical
size, but providing an air gap, for example by means of a
non-magnetic film, between the ends of the limbs and the second
part 43. The person skilled in the art is familiar with measures
making it possible to obtain the desired inductance L of the
respective coupling means 31 to 42, for example by provision of
suitable air gap(s) at the suitable locations.
[0069] Construction of the Phases
[0070] It is particularly advantageous in terms of production
engineering to use just two geometrical shapes of the phases 11 to
16, as illustrated in the plan view in FIG. 5. In this case, one
basic shape has a U-shaped course and lie in the same plane. The
second basic shape is substantially rectangular or meandering,
likewise lying in the same plane. The sections shown can be
integrated as strip conductors in the form of leadframes or in
corresponding conductor tracks in a circuit board. As described in
conjunction with FIGS. 3 and 6, the U-shaped phases 11, 13, 15 are
arranged with respect to one another such that they become situated
on a first plane. Correspondingly, the rectangular or meandering
phases 12, 14, 16, 17 are also arranged such that they become
situated on a second plane. These two planes are arranged parallel
to and spaced apart from one another such that the phase sections
that are respectively to be coupled can be surrounded by the
coupling means 31 to 42.
[0071] In principle, however, alternative configurations of the
phase shapes would also be conceivable, without departing from the
basic concept of the preferably planar construction.
[0072] In particular, certain adaptations are conceivable in order
to further reduce the space requirement of the overall arrangement.
Corresponding variants are depicted schematically in FIGS. 10 and
11. What is intended to be achieved by means of a corresponding
configuration of the geometry of the phases 11 to 17 is that the
coupling means 31 to 42 can be arranged closer to the respectively
adjacent coupling means 31 to 42. This can be achieved, for
example, in accordance with the exemplary embodiment according to
FIG. 10 by virtue of the fact that the ends of the busbars of the
phases 11 to 16 are folded in folding regions 60 indicated by
arrows. As soon as the coupled phase regions (such regions which
are surrounded by the coupling means 31 to 42) leave the coupling
means 31 to 42, the direction changes relative to that within the
coupling means 31 to 42. As a result, the coupling means, in FIG.
10 those bearing the reference signs 39, 35; 35, 34; 32, 38; 38,
33, can move closer together. This is achieved by the phase
sections of the second phase 12 and of the fifth phase 15 being
folded at the end side by a specific angle, for example 45.degree..
The sections of the fifth phase 15 and of the sixth phase 16 prior
to entry into the fifth coupling means 35 are likewise folded by
45.degree., thereby avoiding contact with the second phase 12. As a
result, ninth coupling means 39 and fifth coupling means 35 can be
arranged at a smaller distance from one another than if the phase
sections are led out without folding. In this case, the meandering
busbars of the respective phases 11 to 16 can also be bent up at
the sides. As a result, the meanders can also be pushed into one
another, as illustrated in the left-hand lateral schematic diagram
with plan view. The U-shaped leadframes of the third and fifth
phases 13, 15 would then have to be shifted into different planes,
however, for example by corresponding bending.
[0073] In the case of the exemplary embodiment in accordance with
FIG. 11, the phases 12, 14, 16 running in a meandering fashion are
provided with chamfer regions 62 at the curves or corners, such
that preferably straight sections arise, in order to lead adjacent
phases 12, 16 parallel to one another at a small distance in said
chamfer regions 62. As a result, the coupling means 32, 38 or 39,
35 can likewise be pushed closer together. However, the adjacent
phases (for example the phase sections 12, 16 in accordance with
FIG. 11) can be arranged on the same plane.
[0074] Further possible embodiments extend to arrangements
comprising more than six phases, such as, for example, seven phases
with the exemplary arrangement in matrix form as shown in FIG. 6.
Eight phases would also be possible, distributed among 4-by-4
coupling means. What is essential, however, is that the number of
phases permits independent driving.
[0075] A further magnetic coupling of the individual cores of the
coupling means 31 to 39 to form a large overall core can lead to
further savings, for example by the provision of a single covering
plate 43 for all lower parts of the nine coupling means 31 to
39.
[0076] The multiphase converter 10 described is suitable, in
particular, for use in an on-board electrical system of a motor
vehicle, in which, in particular, dynamic load requirements are of
secondary importance. The construction described is suitable, in
particular, for such comparatively sluggish systems.
* * * * *